Charged particle beam apparatuses have many functions in a plurality of industrial fields, including, but not limited to, inspection of semiconductor devices during manufacturing, exposure systems for lithography, detecting devices and testing systems. Thus, there is a high demand for structuring and inspecting specimens within the micrometer and nanometer scale.
Micrometer and nanometer scale process control, inspection or structuring, is often done with charged particle beams, e.g. electron beams, which are generated and focused in charged particle beam devices, such as electron microscopes or electron beam pattern generators. Charged particle beams offer superior spatial resolution compared to, e.g. photon beams due to their short wavelengths.
Besides resolution, throughput is an issue of such devices. Since large substrate areas have to be patterned or inspected, throughput of for example larger than 10 cm2/min and, therefore, high probe currents in the range of 100 nA or higher, are desirable.
However, particle-particle interaction (Boersch effect) limits the resolution for high beam currents. Especially for low voltage applications, that are applications with the beam energy around or below 1 keV, particle interaction limits the resolution for high beam currents.
One approach for reducing the particle-particle interaction for a lithography systems was proposed by U.S. Pat. No. 6,635,891. Therein, a hollow-beam apparatus utilizing a ring aperture in a crossover is suggested.
However, the hollow beam is difficult to shape and the charged particle interaction might not be significantly reduced.